A variety of different pumps may be employed to pump fluids. For example, diaphragm pumps (which typically include an oscillating membrane together with valves), Knudsen pumps, getter and sputter pumps, roots blowers, and turbo pumps may be employed for this purpose.
For a variety of reasons, however, these exemplary pumps suffer from shortcomings that render them unsuitable or undesirable for MEMS. More specifically, diaphragm pumps typically require mechanical valves, which are difficult to fabricate in a MEMS process. Knudsen pumps generally use a thermal gradient to pump gases, and require high power to operate. For their part, getter and sputter pumps typically use a consumable reactive electrode. When this electrode is used up, the pump stops working. Finally, roots blowers and turbo pumps are not yet capable of being fabricated by MEMS technology.
Fluidic valves for use in MEMS devices suffer from many of the same problems. For example, these valves may include moving parts that are difficult to fabricate and/or wear out over time. MEMS fluidic valves may also experience backflow or leakage issues.
Accordingly, there is a need for improved MEMS pumps and valves that consume low power, are simple to operate, have few or no moving mechanical parts, provide precisely controllable pumping rates (in the case of a MEMS pump), and have no backflow or leakage path.